This application relates generally to methods and systems for performing biometric identifications. More specifically, this application relates to methods and systems for performing biometric identification of individuals using linear optical spectroscopy.
Biometric identification describes the process of using one or more physical or behavioral features to identify a person or other biological entity. There are two common modes in which biometric identification occurs: one-to-many (identification) and one-to-one (verification). One-to-many identification attempts to answer the question of, xe2x80x9cdo I know you?xe2x80x9d The biometric measurement device collects a set of biometric data from a target individual. From this information alone it assesses whether the person was previously enrolled in the biometric system. Systems that perform the one-to-many identification task such as the FBI""s Automatic Fingerprint Identification System (AFIS) are generally very expensive (several million dollars or more) and require many minutes to detect a match between an unknown sample and a large database containing hundreds of thousands or millions of entries. The one-to-one mode of biometrics answers the question of, xe2x80x9care you who you say you are?xe2x80x9d This mode is used in cases where an individual makes a claim of identity using a code, magnetic card, or other means, and the device uses the biometric data to confirm the identity of the person by comparing the target biometric data with the enrolled data that corresponds with the purported identity.
There also exists at least one variant between these two modes. This variant occurs in the case where a small number of individuals are contained in the enrolled database and the biometric application requires the determination of only whether a target individual is among the enrolled set. In this case, the exact identity of the individual is not required and thus the task is somewhat different (and often easier) than the identification task described above. This variant might be useful in applications where the biometric system is used to secure an expensive, dangerous, or complex piece of machinery. In this example, only authorized people should be able to use the equipment, but it might not be of interest to determine specifically which of the authorized personnel are using it at a particular time.
Although in general the one-to-many identification task is more difficult than one-to-one, the two tasks become the same as the number of recognized or authorized users for a given biometric device decreases to just a single individual. Situations in which a biometric identification task has only a small number of entries in the authorization database are quite common. For example, biometric access to a residence, to a personal automobile, to a personal computer, to a cellular telephone, to a handgun, and other such personal devices typically require an authorization database of just a few people.
Biometric identification and verification are useful in many applications. Examples include verifying identity prior to activating machinery or gaining entry to a secure area. Another example would be identification for matching an individual to records on file for that individual, such as for matching hospital patient records when the individual""s identity is unknown. Biometric identification is also useful to match police records at the time a suspect is apprehended, but true identity of the suspect is not known. Additional uses of biometric identification or verification include automotive keyless start and entry applications, secure computer and network access, automated financial transactions, authorized handgun use, and time-and-attendance applications.
Current methods for biometric identification are manifold, but some of the most common techniques include fingerprint pattern matching, facial recognition, hand geometry, iris scanning, and voice recognition. Each of these technologies addresses the need for biometric identification to some extent. However, due to cost, performance, or other issues, each of the existing methods has advantages and disadvantages relative to the other technologies.
One present biometric product on the market is known as the LiveGrip(trademark), made by Advanced Biometrics, Inc. This product is based on the technology disclosed in U.S. Pat. No. 5,793,881, by Stiver et al. In this patent, Stiver et al. disclose an identification system that is a security device, which consists of a cylindrical or elongated transparent shell with an internal light source and a means to scan the hand of the person grasping the shell to record the internal structure or subcutaneous structure of the hand using an imaging methodology. The system uses near-infrared light to image the pattern of blood vessels and associated tissue in the hand. The LiveGrip product based on this patent is claimed to have reduced the ability for an intruder to fool the biometric system as they claim can be easily done using a latex mold with many finger print readers or hand-geometry systems. However, the imaging approach requires good quality optics and/or detector arrays that add to both system complexity and cost. Further, the system relies on imaging blood vessels, and therefore, requires that the same site be presented to the system in use as during enrollment and further requires that the repositioning of the site is accurate enough to allow the software to align the two images to confirm identity. Finally, the size of the sensor head is limited to the portion of the hand that must be imaged for accurate identification.
Others in the field have disclosed methods and systems for measuring properties of samples based on an optical nonlinearity associated with the depletion of the density of states that depends on the presence and magnitude of multiple simultaneous wavelengths of illumination light. In some cases these nonlinear optical spectroscopic sensors are mounted on linear potentiometers and are adjusted to measure the optical properties of the tissue between consecutive pairs of fingers. The resulting measurements from potentiometers are combined with the measurements from the nonlinear optical probes to act as inputs into an identification process.
Living human tissue is recognized as a dynamic system containing a multitude of components and analyte information that is particularly useful in the medical profession for diagnosing, treating and monitoring human physical conditions. To this end, effort has been directed toward developing methods for non-invasive measurement of tissue constituents using spectroscopy. The spectrographic analysis of living tissue has been focused on the identification of spectral information that defines individual analytes and relates such spectral data to the analyte""s concentration. Concentrations of these analytes vary with time in an individual person. Acquiring tissue spectral data with sufficient accuracy for use in diagnosis and treatment has proven difficult. Difficulties in conducting the analysis have been found that are related to the fact that the tissue system is a complex matrix of materials with differing refractive indices and absorption properties. Further, because the constituents of interest are many times present at very low concentrations, high concentration constituents, such as water, have had a detrimental impact on identifying the low level constituent spectral information and giving an accurate reading of the desired constituent concentration. Development of these techniques has always focused on the changes in spectral output with change in concentration of a dynamic analyte of interest, such as glucose. The techniques disclosed are focused on identifying concentrations of specific analytes, the concentration of which is expected to vary with time.
Improved methods and apparatus for gathering and analyzing a near-infrared tissue spectrum for an analyte concentration are disclosed in the following U.S. Patent applications and issued patents, each of which is incorporated herein by reference in its entirety: U.S. Pat. Nos. 5,655,530 and 5,823,951 relate to near-infrared analysis of a tissue analyte concentration that varies with time, with a primary focus on glucose concentrations in diabetic individuals; U.S. Pat. No. 6,152,876 discloses additional improvements in non-invasive living tissue analyte analysis.
U.S. Pat. No. 5,636,633, the entire disclosure of which is incorporated herein by reference, relates, in part, to another aspect of accurate non-invasive measurement of an analyte concentration. The apparatus includes a device having transparent and reflective quadrants for separating diffuse reflected light from specular reflected light. Incident light projected into the skin results in specular and diffuse reflected light coming back from the skin. Specular reflected light has little or no useful information and is preferably removed prior to collection. U.S. Pat. No. 5,935,062, the entire disclosure of which has been incorporated herein by reference, discloses a further improvement for accurate analyte concentration analysis which includes a blocking blade device for separating diffuse reflected light from specular reflected light. The blade allows light from the deeper, inner dermis layer to be captured, rejecting light from the surface, epidermis layer, where the epidermis layer has much less analyte information than the inner dermis layer, and contributes noise. The blade traps specular reflections as well as diffuse reflections from the epidermis.
U.S. Pat. No. 5,435,309, the entire disclosure of which is incorporated herein by reference, relates to a system for selecting optimal wavelengths for multivariate spectral analysis. The use of only one wavelength gives insufficient information, especially for solutions having multiple components. The use of too many wavelengths can include too much noise and lead to combinatorial explosion in calculations. Therefore, the number of wavelengths used should be limited and the wavelengths well chosen. Genetic algorithms are used in this reference to select the most fit wavelengths.
Embodiments of the invention provide method and systems for performing biometric identifications that avoid some deficiencies of the prior art. Some of these embodiments make use of a linear spectroscopic analysis that permits an unexpectedly simple and reliable technique for performing the biometric identifications. Some embodiments are generally applicable to a wide range of biometric tasks, which include identifying individuals (either humans or animals), verifying purported identities of individuals, verifying the liveness of tissue, as well as providing or denying access on the basis of such assessments.
Thus, in a first set of embodiments, a method is provided for identifying an individual. Electromagnetic radiation is propagated into tissue of the individual. A measured spectral variation is received in the form of electromagnetic radiation scattered from the tissue of the individual. The received radiation may thus be reflected by or transmitted through the tissue, or combinations thereof. The measured spectral variation is compared with a previously stored spectral variation over a predetermined wavelength interval. The wavelength interval may alternatively be defined in terms of a frequency interval or any other equivalent measure. The comparison is performed at each of a plurality of wavelengths within the predetermined wavelength interval and is performed of a property of the measured and previously stored spectral variations that is independent of a presence of other wavelengths. The individual is designated as having an identity associated with the previously stored spectral variation if the measured spectral variation is consistent with the previously stored spectral variation.
In some embodiments, the property is an amplitude of the measured and previously stored spectral variations at each of the plurality of wavelengths. In such instances, the comparison may be performed by calculating a discriminant spectral variation at each of the plurality of wavelengths from the measured and previously stored spectral variations at the each of the plurality of wavelengths. The discriminant spectral variation may correspond, for example, to a wavelength-by-wavelength difference of the measured and previously stored spectral variations. Alternatively, the discriminant spectral variation may correspond to a wavelength-by-wavelength ratio of the measured and previously stored spectral variations. Comparing the measured spectral variation with the previously stored spectral variation may further comprise determining whether the discriminant spectral variation is consistent with a calibration database of intraperson difference spectra substantially lacking in interperson spectral differences. In one embodiment, the calibration database comprises spectral differences derived from a plurality of combinations of spectral variations over different conditions from a single individual.
Propagating the electromagnetic radiation into the tissue of the individual may comprise propagating a broad spectral band or may comprise propagating a plurality of signals having different wavelength characteristics. In one embodiment, a time-varying sequence of wavelengths is propagated.
Designating the individual as having an identity associated with the previously stored spectral variation may take place in different ways in different embodiments. For example, in one instance, a purported identity of the individual is obtained, and the previously stored spectral variation corresponds to a spectral variation associated with the purported identity. In such instances, designating the individual as having the identity associated with the previously stored spectral variation thereby corresponds to verifying the purported identity of the individual. In other instances, the previously stored spectral variation may be comprised by a plurality of previously stored spectral variations, with the comparison comprising comparing the measured spectral variation with each of the plurality of previously stored spectral variations. In such instances, the identification may be performed without any input from the individual other than the biometric measurement.
In another set of embodiments, a method is provided for implementing a biometric task with respect to an individual. A spectral variation of electromagnetic radiation is measured from subepidermal tissue from at least one site of the individual. A linear spectroscopic analysis is performed of the spectral variation. The biometric task is performed in accordance with a result of the linear spectroscopic analysis. Performing the biometric task may comprise performing a comparison with a database to identify the individual.
There are a variety of sites that are particularly suitable. For example, in one embodiment, the at least one site comprises at least one of a dorsal and ventral surface of a proximal phalange of a finger or thumb of the individual. In another embodiment, the at least one site comprises at least one of a dorsal and ventral surface of a medial phalange of a finger of the individual. In a further embodiment, the at least one site comprises at least one of a dorsal and ventral surface of a distal phalange of a finger or thumb of the individual. In another embodiment, the at least one site comprises at least one of a dorsal and ventral surface of a wrist of the individual. In still a further embodiment, the at least one surface comprises a web between an index finger and thumb of the individual. In yet another embodiment, the at least one surface comprises a thenar eminence of the individual. In a further embodiment, the at least one site comprises a hypothenar eminence of the individual. In a different embodiment, the at least one site comprises a medial hypothenar eminence of the individual.
The methods of the invention may be embodied in a system. The apparatus includes a source of electromagnetic radiation adapted to propagate radiation into tissue of the individual, as well as a receiver adapted to receive a measured spectral variation in the form of electromagnetic radiation scattered from the tissue of the individual. A spectral-variation database is also provided with a previously stored spectral variation. A computer-readable storage medium is coupled with a processor, the computer-readable storage medium having a computer-readable program embodied therein for directing operation of the processor. The computer-readable program includes instructions for operating the apparatus to identify an individual in accordance with the embodiments described above.